- 16 Mar, 2020 40 commits
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Sean Christopherson authored
Mask kvm_cpu_caps based on host CPUID in preparation for overriding the CPUID results during KVM_GET_SUPPORTED_CPUID instead of doing the masking at runtime. Note, masking may or may not be necessary, e.g. the kernel rarely, if ever, sets real CPUID bits that are not supported by hardware. But, the code is cheap and only runs once at load, so an abundance of caution is warranted. No functional change intended. Reviewed-by:
Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by:
Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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Sean Christopherson authored
Remove the code for handling stateful CPUID 0x2 and mark the associated flags as deprecated. WARN if host CPUID 0x2.0.AL > 1, i.e. if by some miracle a host with stateful CPUID 0x2 is encountered. No known CPU exists that supports hardware accelerated virtualization _and_ a stateful CPUID 0x2. Barring an extremely contrived nested virtualization scenario, stateful CPUID support is dead code. Suggested-by:
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Sean Christopherson authored
Rework CPUID 0x2.0 to be a normal CPUID leaf if it returns "01" in AL, i.e. EAX & 0xff, as a step towards removing KVM's stateful CPUID code altogether. Long ago, Intel documented CPUID 0x2.0 as being a stateful leaf, e.g. a version of the SDM circa 1995 states: The least-significant byte in register EAX (register AL) indicates the number of times the CPUID instruction must be executed with an input value of 2 to get a complete description of the processors's caches and TLBs. The Pentium Pro family of processors will return a 1. A 2000 version of the SDM only updated the paragraph to reference Intel's new processory family: The first member of the family of Pentium 4 processors will return a 1. Fast forward to the present, and Intel's SDM now states: The least-significant byte in register EAX (register AL) will always return 01H. Software should ignore this value and not interpret it as an information descriptor. AMD's APM simply states that CPUID 0x2 is reserved. Given that CPUID itself was introduced in the Pentium, odds are good that the only Intel CPU family that *maybe* implemented a stateful CPUID was the P5. Which obviously did not support VMX, or KVM. In other words, KVM's emulation of a stateful CPUID 0x2.0 has likely been dead code from the day it was introduced. This is backed up by commit 0fdf8e59 ("KVM: Fix cpuid iteration on multiple leaves per eac"), which shows that the stateful iteration code was completely broken when it was introduced by commit 07716717 ("KVM: Enhance guest cpuid management"), i.e. not actually tested. Annotate all stateful code paths as "unlikely", but defer its removal to a future patch to simplify reinstating the code if by some miracle there is someone running KVM on a CPU with a stateful CPUID 0x2. Reviewed-by:
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Sean Christopherson authored
Explicitly handle CPUID 0x7 sub-leaf 1. The kernel is currently aware of exactly one feature in CPUID 0x7.1, which means there is room for another 127 features before CPUID 0x7.2 will see the light of day, i.e. the looping is likely to be dead code for years to come. Reviewed-by:
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Sean Christopherson authored
Move the CPUID 0x7 masking back into __do_cpuid_func() now that the size of the code has been trimmed down significantly. Tweak the WARN case, which is impossible to hit unless the CPU is completely broken, to break the loop before creating the bogus entry. Opportunustically reorder the cpuid_entry_set() calls and shorten the comment about emulation to further reduce the footprint of CPUID 0x7. Reviewed-by:
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Sean Christopherson authored
Set UMIP in kvm_cpu_caps when it is emulated by VMX, even though the bit will effectively be dropped by do_host_cpuid(). This allows checking for UMIP emulation via kvm_cpu_caps instead of a dedicated kvm_x86_ops callback. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Add accessor(s) for KVM cpu caps and use said accessor to detect hardware support for LA57 instead of manually querying CPUID. Note, the explicit conversion to bool via '!!' in kvm_cpu_cap_has() is technically unnecessary, but it gives people a warm fuzzy feeling. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Add a helper, kvm_cpu_cap_check_and_set(), to query boot_cpu_has() as part of setting a KVM cpu capability. VMX in particular has a number of features that are dependent on both a VMCS capability and kernel support. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Move the clearing of the XSAVES CPUID bit into VMX, which has a separate VMCS control to enable XSAVES in non-root, to eliminate the last ugly renmant of the undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in the common CPUID handling code. Drop ->xsaves_supported(), CPUID adjustment was the only user. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Use the recently introduced KVM CPU caps to propagate VMX-only (kernel) settings to supported CPUID flags. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Use the recently introduced KVM CPU caps to propagate SVM-only (kernel) settings to supported CPUID flags. Note, there are a few subtleties: - Setting a flag based on a *different* feature is effectively emulation, and must be done at runtime via ->set_supported_cpuid(). - CPUID 0x8000000A.EDX is a feature leaf that was previously not adjusted by kvm_cpu_cap_mask() because all features are hidden by default. Opportunistically add a technically unnecessary break and fix an indentation issue in svm_set_supported_cpuid(). No functional change intended. Reviewed-by: -
Sean Christopherson authored
Calculate the CPUID masks for KVM_GET_SUPPORTED_CPUID at load time using what is effectively a KVM-adjusted copy of boot_cpu_data, or more precisely, the x86_capability array in boot_cpu_data. In terms of KVM support, the vast majority of CPUID feature bits are constant, and *all* feature support is known at KVM load time. Rather than apply boot_cpu_data, which is effectively read-only after init, at runtime, copy it into a KVM-specific array and use *that* to mask CPUID registers. In additional to consolidating the masking, kvm_cpu_caps can be adjusted by SVM/VMX at load time and thus eliminate all feature bit manipulation in ->set_supported_cpuid(). Opportunistically clean up a few warts: - Replace bare "unsigned" with "unsigned int" when a feature flag is captured in a local variable, e.g. f_nx. - Sort the CPUID masks by function, index and register (alphabetically for registers, i.e. EBX comes before ECX/EDX). - Remove the superfluous /* cpuid 7.0.ecx */ comments. No functional change intended. Signed-off-by: -
Sean Christopherson authored
Invert the handling of XSAVES, i.e. set it based on boot_cpu_has() by default, in preparation for adding KVM cpu caps, which will generate the mask at load time before ->xsaves_supported() is ready. No functional change intended. Reviewed-by:
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Paolo Bonzini authored
The clearing of the GBPAGE CPUID bit for VMX is wrong; support for 1GB pages in EPT has no relationship to whether 1GB pages should be marked as supported in CPUID. This has no ill effect because we're only clearing the bit, but we're not marking 1GB pages as available when EPT is disabled (even though they are actually supported thanks to shadowing). Instead, forcibly enable 1GB pages in the shadow paging case. This also eliminates an instance of the undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in the common CPUID handling code, and paves the way toward eliminating ->get_lpage_level(). Signed-off-by: -
Sean Christopherson authored
Move the Processor Trace CPUID adjustment into VMX code to eliminate an instance of the undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in the common CPUID handling code, and to pave the way toward eventually removing ->pt_supported(). No functional change intended. Reviewed-by:
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Sean Christopherson authored
Move the clearing of the RDTSCP CPUID bit into VMX, which has a separate VMCS control to enable RDTSCP in non-root, to eliminate an instance of the undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in the common CPUID handling code. Drop ->rdtscp_supported() since CPUID adjustment was the last remaining user. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Move the setting of the PKU CPUID bit into VMX to eliminate an instance of the undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in the common CPUID handling code. Drop ->pku_supported(), CPUID adjustment was the only user. Note, some AMD CPUs now support PKU, but SVM doesn't yet support exposing it to a guest. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Move the CPUID adjustment for UMIP emulation into VMX code to eliminate an instance of the undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in the common CPUID handling code. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Move the INVPCID CPUID adjustments into VMX to eliminate an instance of the undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in the common CPUID handling code. Drop ->invpcid_supported(), CPUID adjustment was the only user. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Move the MPX CPUID adjustments into VMX to eliminate an instance of the undesirable "unsigned f_* = *_supported ? F(*) : 0" pattern in the common CPUID handling code. Note, to maintain existing behavior, VMX must manually check for kernel support for MPX by querying boot_cpu_has(X86_FEATURE_MPX). Previously, do_cpuid_7_mask() masked MPX based on boot_cpu_data by invoking cpuid_mask() on the associated cpufeatures word, but cpuid_mask() runs prior to executing vmx_set_supported_cpuid(). No functional change intended. Reviewed-by:
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Sean Christopherson authored
Use the recently introduced cpuid_entry_get_reg() to automatically get the appropriate register when masking a CPUID entry. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Introduce mutators to modify feature bits in CPUID entries and use the new mutators where applicable. Using the mutators eliminates the need to manually specify the register to modify query at no extra cost and will allow adding runtime consistency checks on the function/index in a future patch. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Introduce accessors to retrieve feature bits from CPUID entries and use the new accessors where applicable. Using the accessors eliminates the need to manually specify the register to be queried at no extra cost (binary output is identical) and will allow adding runtime consistency checks on the function and index in a future patch. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Replace "unsigned" with "unsigned int" to make checkpatch and people everywhere a little bit happier, and to avoid propagating the filth when future patches add more cpuid helpers that work with unsigned (ints). No functional change intended. Suggested-by:
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Sean Christopherson authored
Change the intermediate CPUID output register values from "int" to "u32" to match both hardware and the storage type in struct cpuid_reg. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Drop the explicit @func param from ->set_supported_cpuid() and instead pull the CPUID function from the relevant entry. This sets the stage for hardening guest CPUID updates in future patches, e.g. allows adding run-time assertions that the CPUID feature being changed is actually a bit in the referenced CPUID entry. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Clear the output regs for the main CPUID 0x14 leaf (index=0) if Intel PT isn't exposed to the guest. Leaf 0x14 enumerates Intel PT capabilities and should return zeroes if PT is not supported. Incorrectly reporting PT capabilities is essentially a cosmetic error, i.e. doesn't negatively affect any known userspace/kernel, as the existence of PT itself is correctly enumerated via CPUID 0x7. Reviewed-by:
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Sean Christopherson authored
Expose kvm_mpx_supported() as a static inline so that it can be inlined in kvm_intel.ko. No functional change intended. Reviewed-by:
Xiaoyao Li <xiaoyao.li@intel.com> Reviewed-by:
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Sean Christopherson authored
Query supported_xcr0 when checking for MPX support instead of invoking ->mpx_supported() and drop ->mpx_supported() as kvm_mpx_supported() was its last user. Rename vmx_mpx_supported() to cpu_has_vmx_mpx() to better align with VMX/VMCS nomenclature. Modify VMX's adjustment of xcr0 to call cpus_has_vmx_mpx() (renamed from vmx_mpx_supported()) directly to avoid reading supported_xcr0 before it's fully configured. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Add a new global variable, supported_xcr0, to track which xcr0 bits can be exposed to the guest instead of calculating the mask on every call. The supported bits are constant for a given instance of KVM. This paves the way toward eliminating the ->mpx_supported() call in kvm_mpx_supported(), e.g. eliminates multiple retpolines in VMX's nested VM-Enter path, and eventually toward eliminating ->mpx_supported() altogether. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Add helpers to query which of the (two) supported PT modes is active. The primary motivation is to help document that there is a third PT mode (host-only) that's currently not supported by KVM. As is, it's not obvious that PT_MODE_SYSTEM != !PT_MODE_HOST_GUEST and vice versa, e.g. that "pt_mode == PT_MODE_SYSTEM" and "pt_mode != PT_MODE_HOST_GUEST" are two distinct checks. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Use __do_cpuid_func()'s common loop iterator, "i", when enumerating the sub-leafs for CPUID 0xD now that the CPUID 0xD loop doesn't need to manual maintain separate counts for the entries index and CPUID index. No functional changed intended. Reviewed-by:
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Sean Christopherson authored
Drop a "nent >= maxnent" check in kvm_get_cpuid() that's fully redundant now that kvm_get_cpuid() isn't indexing the array to pass an entry to do_cpuid_func(). Reviewed-by:
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Sean Christopherson authored
Add a struct to hold the array of CPUID entries and its associated metadata when handling KVM_GET_SUPPORTED_CPUID. Lookup and provide the correct entry in do_host_cpuid(), which eliminates the majority of array indexing shenanigans, e.g. entries[i -1], and generally makes the code more readable. The last array indexing holdout is kvm_get_cpuid(), which can't really be avoided without throwing the baby out with the bathwater. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Refactoring the sub-leaf handling for CPUID 0x4/0x8000001d to eliminate a one-off variable and its associated brackets. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Declare "i" and "max_idx" at the top of __do_cpuid_func() to consolidate a handful of declarations in various case statements. More importantly, establish the pattern of using max_idx instead of e.g. entry->eax as the loop terminator in preparation for refactoring how entry is handled in __do_cpuid_func(). No functional change intended. Reviewed-by:
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Sean Christopherson authored
Move the nent vs. maxnent check and nent increment into do_host_cpuid() to consolidate what is now identical code. To signal success vs. failure, return the entry and NULL respectively. A future patch will build on this to also move the entry retrieval into do_host_cpuid(). No functional change intended. Reviewed-by:
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Sean Christopherson authored
Drop redundant checks when "emulating" SSBD feature across vendors, i.e. advertising the AMD variant when running on an Intel CPU and vice versa. Both SPEC_CTRL_SSBD and AMD_SSBD are already defined in the leaf-specific feature masks and are *not* forcefully set by the kernel, i.e. will already be set in the entry when supported by the host. Functionally, this changes nothing, but the redundant check is confusing, especially when considering future patches that will further differentiate between "real" and "emulated" feature bits. No functional change intended. Reviewed-by:
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Sean Christopherson authored
Drop the index param from do_cpuid_7_mask() and instead switch on the entry's index, which is guaranteed to be set by do_host_cpuid(). No functional change intended. Reviewed-by:
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Sean Christopherson authored
Refactor the sub-leaf loop for CPUID 0x7 to move the main leaf out of said loop. The emitted code savings is basically a mirage, as the handling of the main leaf can easily be split to its own helper to avoid code bloat. No functional change intended. Reviewed-by:
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